netdev - Re: [patch net-next 06/11] net: devlink: don't take devlink_mutex for devlink_compat

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Date:   Thu, 21 Mar 2019 12:08:24 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, mlxsw@...lanox.com,
        idosch@...lanox.com, f.fainelli@...il.com, andrew@...n.ch,
        vivien.didelot@...il.com
Subject: Re: [patch net-next 06/11] net: devlink: don't take devlink_mutex
 for devlink_compat_*

On Thu, 21 Mar 2019 14:20:14 +0100, Jiri Pirko wrote:
> From: Jiri Pirko <jiri@...lanox.com>
> 
> The netdevice is guaranteed to not disappear so we can rely that
> devlink_port and devlink won't disappear as well. No need to take
> devlink_mutex so don't take it here.

I'm not sure the port can't disappear, just looking at this series it
seems bnxt registers the port after netdev (maybe it unregisters in 
the other order).  Not that it matters here, we use the main devlink
instance for the compat helpers, and devlink instance should
definitely exist.

So FWIW the entire series looks good to me.

I've also pushed my port patches out:

https://git.kernel.org/pub/scm/linux/kernel/git/kuba/linux.git/log/?h=devlink-pci-ports

if that's of any use to you (e.g. the patch which changes the order of
port vs netdev registration).

> Signed-off-by: Jiri Pirko <jiri@...lanox.com>

> diff --git a/net/core/devlink.c b/net/core/devlink.c
> index 3dc51ddf7451..1e125c3b890c 100644
> --- a/net/core/devlink.c
> +++ b/net/core/devlink.c
> @@ -6444,17 +6444,15 @@ void devlink_compat_running_version(struct net_device *dev,
>  	dev_hold(dev);
>  	rtnl_unlock();
>  
> -	mutex_lock(&devlink_mutex);
>  	devlink = netdev_to_devlink(dev);
>  	if (!devlink || !devlink->ops->info_get)
> -		goto unlock_list;
> +		goto out;
>  
>  	mutex_lock(&devlink->lock);
>  	__devlink_compat_running_version(devlink, buf, len);
>  	mutex_unlock(&devlink->lock);
> -unlock_list:
> -	mutex_unlock(&devlink_mutex);
>  
> +out:
>  	rtnl_lock();
>  	dev_put(dev);
>  }
> @@ -6462,22 +6460,22 @@ void devlink_compat_running_version(struct net_device *dev,
>  int devlink_compat_flash_update(struct net_device *dev, const char *file_name)
>  {
>  	struct devlink *devlink;
> -	int ret = -EOPNOTSUPP;
> +	int ret;
>  
>  	dev_hold(dev);
>  	rtnl_unlock();
>  
> -	mutex_lock(&devlink_mutex);
>  	devlink = netdev_to_devlink(dev);
> -	if (!devlink || !devlink->ops->flash_update)
> -		goto unlock_list;
> +	if (!devlink || !devlink->ops->flash_update) {
> +		ret = -EOPNOTSUPP;
> +		goto out;
> +	}
>  
>  	mutex_lock(&devlink->lock);
>  	ret = devlink->ops->flash_update(devlink, file_name, NULL, NULL);
>  	mutex_unlock(&devlink->lock);
> -unlock_list:
> -	mutex_unlock(&devlink_mutex);
>  
> +out:
>  	rtnl_lock();
>  	dev_put(dev);
>